* {
    margin: 0;
    padding: 0;
}
ul {
    list-style: none;
}
nav {
    height: 42px;
    background-color: rgba(0,139,139,0.3);
    text-align: center;
}
.menu {
    /*设置弹性盒子*/
    display: flex;
    justify-content: center;
}
.menu> li .a{
    border-left:1px solid rgb(247, 252, 255);
}
.a {
    text-decoration: none;
    color: #fff;
    display: block;
    padding: 10px 15px;
    font-size: 16px;
    transition: background-color 0.5s ease-in-out;
}
.a:hover {
    background-color:#631818;
}
.kind li{
    opacity: 0;
    transform-origin: top center;
}
.kind li .a {
    background-color: rgba(0,139,139,0.3);
    padding: 10px 0;
}

